(CNN) -- An Oregon State Police bomb technician became the second victim of a bomb in a Woodburn bank branch, State Police spokesman Lt. Gregg Hastings confirmed Saturday.

A bomb technician and a police captain were killed by a bomb inside West Coast Bank in Woodburn, Oregon.

Technician Bill Hakim, a senior trooper, and Woodburn Police Capt. Tom Tennant were killed in Friday evening's blast, Hastings said. Both men were 51 years old.

Woodburn Police Chief Scott Russell, 46, was critically injured. A female bank employee also was injured. She was treated at a hospital and released, the State Police said in a written statement. Her name was not immediately available.

The FBI and the Bureau of Alcohol, Tobacco, Firearms and Explosives are offering a $35,000 reward for information leading to the arrest and conviction of anyone responsible.

The 5:24 p.m. explosion at West Coast Bank came after the nearby Wells Fargo Bank had received a threatening telephone call Friday morning from an unknown person, Oregon State Police said.

When authorities arrived at Wells Fargo Bank, they discovered a "suspicious object" that was later determined not to be dangerous.

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Their investigation led to a suspicious device outside West Coast Bank, and all but two employees were evacuated from the bank, Hastings said. It was not immediately clear why those two employees were not evacuated.

The device was brought inside, and it exploded, Hastings said. He said it was not clear why it had been brought inside.

He said the two bank employees who had not been evacuated were in another part of the bank when the bomb went off. They received minor injuries. One may have been hit by flying debris, and another was "bothered by the sound," Sznewajs said.

Hastings urged anyone with more information about the bomb to come forward.

"This individual or individuals took the life of two police officers and critically injured the chief of police and potentially could have killed one or both of the bank employees that were still inside," Hastings said.

"That person is very dangerous, and that person needs to be found as soon as possible," he said. "And if it takes a $35,000 reward, or if that reward even grows, to convince someone to come forward, to give us that information that's going to break the case, then that's money well spent."

Sznewajs said there had been no previous incidents or threats at the bank.

"We would keep pretty close track on anything like that," he said. "We haven't had any."

Woodburn Mayor Kathy Figley told reporters Saturday that the deaths of the two law enforcement officers and the wounding of the town's police chief had left residents "shocked and saddened."

Tennant was a 28-year veteran of the police department, and Russell has served as police chief since 1999, she said. Tennant's wife is the town's recorder, or clerk.

"We are talking about people who are our friends, our neighbors," Figley said.

She said that as federal and state agencies investigate the blast other law enforcement agencies have stepped in to support the town and its police department.

"The safety of our community is paramount, and it is in good hands," Figley said.

The Wells branch and the West Coast branch are less than 150 feet apart.

Woodburn is in the Willamette Valley, about 30 miles south of Portland.